The present invention relates to gas discharge displays and, more particularly, to a novel gas discharge display having means for enhancing current sharing between a plurality of electrodes coupled to a common matrix line.
Gas discharge displays of the planar electrode type offer several advantages as low cost displays. In addition to the generally pleasing appearance of such displays, the display format is of relatively great flexibility, in that information display areas may generally be changed by substitution of a mask during the display process step in which conductive electrodes are fabricated on a glass substrate. To provide greater flexibility, the design of a particular gas discharge display will often require that a number of the cathode or anode electrodes of such display be connected together in electrical parallel connection to a common matrix address line. However, it is known that the current drawn by each energized section, or cell, of a gas discharge display is related to the area of the electrodes thereof; the brightness and, subsequently, the contrast of each energized display cell is related to the current drawn thereby. Thus, display areas having electrodes of substantially equal areas will draw substantially equal current and have substantially equal brightness and contrast against the normally-dark background (in which a discharge is not facilitated through the gaseous medium of the display). If the electrode areas are other than substantially equal, the current discharging through the display gas is not equal for all paralleled sections and some means, generally adding to the cost and complexity of the display, is required to promote current-sharing between the several electrodes. It is known that an electrical resistance, placed in series connection between each of the electrodes and the common matrix line of appropriate value, be provided to facilitate such current-sharing at very low cost. It has been impractical to utilize such series resistance current-sharing techniques, due to the requirement that, during manufacture of gas discharge displays, a "run-in" period is required during which relatively greater than normal currents must flow through the display; the high-current "run-in" requirements directly conflict with the requirement for relatively high series resistance for normal-operation current-sharing. It is, therefore, desirable to have a gas discharge display of structure enabling the relatively high current run-in procedure to be utilized, while providing some means for obtaining current-sharing between a plurality of paralleled discharge electrodes comparable to a common display matrix address line.